Perhaps you should try some spelling variations:
chet triet » chuyen triet, thuyet triet
thanh ly » thanh lay, thanh ky, thanh le
ly chet » ly chat, la chet, ly thiet
dua ban » dia ban, qua ban, mua ban
tu sach » thu sach, su sach, te sach
hieu va » lieu va, hieu qua
sach ky » sac ky, sach y, sach ty
va cao » va cac, va co, va dao
o hoc » co hoc, mo hoc, so hoc
o hoi » co hoi, o hai, o hoa

You may be able to get more results by adjusting your search query.

• Performing a fuzzy search may retrieve terms with similar spellings: tu sach ky nang ((o hoi) or (o hoc)). hieu va cao ((dua ban) OR (cua ban)) thanh ly chet triet~.
• If you are trying to use Boolean operators, they must be ALL CAPS: tu sach ky nang ((o hoi) OR (o hoc)). hieu va cao ((dua ban) OR (cua ban)) thanh ly chet triet*.
• The words AND, OR and NOT may confuse the search; try adding quotes: "tu sach ky nang ((o hoi) or (o hoc)). hieu va cao ((dua ban) OR (cua ban)) thanh ly chet triet*".